Actuator

ABSTRACT

An actuating device comprising: a ball screw arrangement having an externally threaded screw and an internally threaded nut engageable with the screw through ball bearings, the nut being longitudinally movable along the screw on rotation of the screw. The screw may be mounted on support means for rotation only. Power means may be connected to the screw through clutch means for rotation thereof to drive the nut longitudinally thereon from a first position to another. The nut is connected to a rotatable member by a mechanism adapted to convert longitudinal movement of the nut to rotational movement of a portion of a device connected to the rotatable member. A spring return unit may be attached so as to exert a force against the nut. The spring return unit may be adapted on disengagement of the clutch to drive the nut back to its first position.

ited States Patent Gtnlick et a1. Feb. 8, 1972 [54] ACTUATOR [72]Inventors: Ronald A. Gulick, Sugarland; Charles H. Pnmary Emmlner-wllllam O Dea [73] Assignee: Research Engineering Company, Houston,

Test.

[22] Filed: June 2, 1969 [21] Appl. No.: 829,523

[52] US. Cl. ..74/89.l5, 74/424.8 VA, 251/71 [51] Int. Cl ..Fl6h 29/02[58} Field of Search ..74/89.15, 509, 424.8 VA; 251/69, 68, 70, 71

[56] References Cited UNITED STATES PATENTS 2,298,717 10/1942 Nardone..74/89.l5 X

3,063,298 11/1962 Elliott ..74/89.15

3,147,766 9/1964 Herring et al. ...74/89.l5 X

3,422,329 1/1969 Anderson et al .251 /69 X Wicke, Richmond, both of Tex.

Assistant Examiner-F. D. Shoemaker Attorney--Robert W. B. DickersonABSTRACT An actuating device comprising: a ball screw arrangement havingan externally threaded screw and an internally threaded nut engageablewith the screw through ball bearings, the nut being longitudinallymovable along the screw on rotation of the screw. The screw may bemounted on support means for rotation only. Power means may be connectedto the screw through clutch means for rotation thereof to drive the nutlongitudinally thereon from a first position to another. The nut isconnected to a rotatable member by a mechanism adapted to convertlongitudinal movement of the nut to rota tional movement of a portion ofa device connected to the rotatable member. A spring return unit may beattached so as to exert a force against the nut. The spring return unitmay be adapted on.disengagement of the clutch-to drive the nut back toits first position. 7

17 Claims, 1 Drawing Figure PATENTED FEB 8I972 ACTUATOR BACKGROUND OFTHE INVENTION 1. Field of the Invention This invention relates toactuators primarily for use in operating valves. Specifically, itconcerns a spring-return-type actuator which may be electricallyactuated.

2. Description of the Prior Art It is well known in the art to provideelectric actuators for operating valves. Electric actuators areparticularly suited for remote and automatic operation. Most electricactuators require switching circuitry for reversing the rotatingdirection of its electric motor in order to open and close a valve.Although this may involve a more complex design, the major disadvantageof such an actuator may be in its inability to fail safe in the event ofpower failure. Thus, a valve may remain in its opened or closed positionat the wrong time. In certain applications this may be both expensiveand hazardous.

SUMMARY OF THE INVENTION In the present invention an electric actuatorfor operating a valve is disclosed which is capable of failing safe inthe event of power failure. It utilizes an electric motor rotating inone direction only. The electric motor may be connected through a clutchunit to the screw of a ball-screw or similar overhauling threadmechanism. The nut of the ball-screw mechanism is attached to a yoke foroperating a valve. Rotation of the screw by the motor causes the nut andvalve stem to move. A spring return mechanism is connected to theball-screw nut and on a signal or power failure, to disengage the clutchunit, returns the nut and valve stem to their initial positions. Otherfeatures of the invention pointed out in the claims can best be setforth in the description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS For a detailed description of apreferred embodiment of the invention, reference will be made to theaccompanying drawing, but this is only exemplary of the invention whichcan be varied by one skilled in the art. The drawing selected fordescription isa plan view partially in section of a preferred embodimentof the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The actuator may be attached tovalve 10 or any other device requiring approximately 90 rotational inputwhich might be operated thereby by a mounting bracket II and bolts 12 orthe like. The particular embodiment shown is for operating plug valvesand similar valves which are operated by a 90 turn of the stem 15.However, it may be adapted for use with other type valves.

The actuator comprises a body portion 20, a clutch unit 30, motor andgear box assembly 40, and spring return assembly 50. Clutch unit 30 isconnected between motor and body 20 by cap screws 31, 32 or the like andthrough this clutch 30 the screw 60 of a ball-screw mechanism may beconnected to motor 40 for rotation.

The construction and operation of ball-screw mechanisms are well known.However, this particular arrangement is believed to be unique. The nut61 of the ball-screw mechanism is mounted within body 20 and attached toa yoke 21 by a pin 62 and slot 22 arrangement. As is well known, thescrew 60 and nut 61 are provided with cooperating thread grooves inwhich are mounted ball bearings 69. As the screw rotates relative to nut61 the nut moves longitudinally along screw 60 and ball bearings 69 arefed from one end of nut 61 to the other through a return tube (notshown). In this particular embodiment a hollow shaft or tube 63 isconnected to nut 61 and mounted around screw 60 for longitudinalmovement with nut 61. Screw 60 is mounted on radial bearing means 65 andthrust bearing means 66 at one end of body 20. The other end of screw 60is mounted in a sliding bearing 67 of a circular spring pressure plate51 which is connected to tube 63 for movement therewith.

In addition to spring pressure plate 51, spring return unit 50 comprisesa cylindrical housing 52, cylinder head 53, a pair of guide rods 54,threadingly connected to body.20, and helical spring 55. Pressure plate51 is mounted on' guide rods 54 for sliding longitudinal motion withinhousing 52.-Sleeve bearings 56, 57 reduce the sliding friction.

Clutch unit 30 comprises a sleeve engagement device 33 mounted on oneend of screw 60 for limited longitudinal movement. A pin 34, attached toscrew 60, and slot 35, in sleeve 33, allows this limited longitudinal.movement but prevents rotation of the sleeve 33 relative to screw 60.Attached to the end of motor assembly output shaft 41 is a clutch hub42. The adjacent ends of hub 42 and sleeve 33 are provided withengageable cooperating sawtooth members so that rotation of shaft 41 inone direction will drive screw 60. The slope of the sawteeth preventreverse drive. Hub 42 and sleeve 33 are held in engagement by a solenoid36. This is accomplished through a lever 37 which is pivotally connectedat 38. Clutch sleeve 33 is provided with a groove 39which slidinglyreceives a pin 44 attached to lever 37. Solenoid 36 may be connected inthe power circuit in such a manner that when motor 40 is energized thesolenoid 36 is also energized. When thesolenoid 36 is energized-itforces clutch sleeve 33 into engagement with clutch jaw 42. Whensolenoid 36 is deenergized lever 37 pivots away from motor 40disengaging the clutch mechanism. I

As shown in the drawing the actuator is in the position of beginning apower stroke. With power supplied to motor 40 and solenoid 36, the motor40 drives or rotates the ball screw 60 through the engaged clutch.Ball-screw nut 61 is driven along screw 60 toward spring 55 causing yoke21 to rotate in body 20. The hub 25 of yoke 21 is keyed to valve stem 15causing it to also rotate and move the valve from a first position to asecond position. As nut 61 is driven along screw 60 it also compressesspring 55 through tube 63 andspring pressure plate 51. When the actuatorreaches its full travel position the power to the motor circuit only maybe broken by a switch (not shown) actuated by yoke 21 at some specifieddegree of rotation. The clutch solenoid 36, remaining under power, holdsthe clutch in its engaged position. The construction of motor and geartrain assembly 40 may be such as to not allow the force of spring 55acting through screw 60 to rotate the motor in reverse when the power isoff. At this point the actuator is at the end of its stroke.

If the power to solenoid 36 is now interrupted purposely or throughpower failure to solenoid 36 the clutch disengages the motor 40 andscrew 60. The screw 60 now being free to rotate allows compressed spring55 to drive ball nut 61 along the screw 60 to its original position. Inthis movement yoke 21 rotates to its original position causing valvestem 15 to assume its original position. The cycle is now complete.

Thus, it can be seen that through the ball-screw mechanism and clutchand spring assembly an electric operator may be provided to assure failsafe operation. This unique arrangement also eliminates the need for areverse rotating motor and provides a relatively simple compactefficient actuator.

We claim:

1. An actuating device comprising: a ball-screw arrangement having ascrew with external thread grooves and a nut with internal threadgrooves engageable with said screw through ball bearings cooperativelyreceived within said external and internal thread grooves, said nutbeing longitudinally movable along said screw on rotation of said screwrelative thereto; support means on which said screw is mounted forrotation only; power means connected to said screw for rotation thereofto drive said nut longitudinally thereon from a first to a secondposition; a rotatable member mounted on said support means adapted forattachment to apparatus to be actuated; a mechanism connecting said nutand said rotating member adapted to convert longitudinal movement ofsaid nut to rotary motion of said rotatable member; spring means mountedso as to bias said nut toward said first-position;

said power means being connected to said screw through clutch means,said clutch means being disengageable to allow rotation of said screw,said spring means being adapted to force said nut along said screw fromsaid second position toward said first position when said clutch isdisengaged.

2. An actuating device comprising: a ball-screw arrangement having ascrew with external thread grooves and a nut with internal threadgrooves engageable with said screw through ball bearings cooperativelyreceived within said external and internal thread grooves, said nutbeing longitudinally movable along said screw on rotation of said screwrelative thereto; support means on which said screw is mounted forrotation only; power means connected to said screw for rotation thereofto drive said nut longitudinally thereon from a first position to asecond position; a rotatable member mounted on said support meansadapted for attachment to apparatus to be actuated; a mechanismconnecting said nut and said rotating member adapted to convertlongitudinal movement of said nut to rotary motion of said rotatablemember; spring means mounted so as to bias said nut toward said firstposition; said spring means comprises a cylindrical housing attached tosaid support means and a helical spring mounted in said housing, one endof said spring bearing against a pressure plate, said pressure platebeing connected to said nut by shaft means so that on movement of saidnut from said first position to said second position said pressure platemoves longitudinally within said housing to compress said spring.

3. An actuating device as set forth in claim 2, characterized by a pairof rods fixedly and longitudinally mounted within said housing, saidpressure plate having a pair of holes through which said rods pass insliding engagement.

4. An actuating device as set forth in claim 2 characterized in thatsaid shaft means comprises a hollow tube surrounding a portion of saidscrew and longitudinally movable thereon with said nut.

5. An actuating device comprising: body means, a ballscrew mechanismhaving a screw mounted longitudinally within said body for rotation onlyand a nut engageable with said screw through ball bearing means andlongitudinally movable along said screw on rotation of said screw; yokemeans mounted in said body means for rotation on an axis substantiallyperpendicular to said screw and adapted for attachment to apparatus tobe actuated; a mechanism connecting said nut and said yoke adapted toconvert longitudinal movement of said nut to rotary movement of saidyoke; power means connected to said screw for rotation thereof to causesaid nut to move longitudinally therealong from a first position to asecond position; spring means mounted on said body adapted to bias saidnut toward said first position, said power means being connected to saidscrew by clutch means, said clutch means being disengageable when saidnut is in said second position to allow said spring means to return saidnut toward said first position.

6. An actuating device as set forth in claim 5, characterized in thatsaid power means comprises an electric motor and said clutch meanscomprises sleeve means, mounted on the end of said screw for limitedlongitudinal movement, and a solenoid, said sleeve means being connectedto said solenoid by a pivoting link, said solenoid being adapted, whenenergized, to pivot said link and move said sleeve means longitudinallyinto engagement with a portion of said clutch connected to said electricmotor.

7. An actuating device as set forth in claim 5, characterized in thatsaid spring means comprises a spring mounted in an elongated housingattached to said body, said spring bearing against a pressure platewhich is connected to said nut by a tube surrounding said screw, saidtube and said pressure plate being longitudinally movable on movement ofsaid nut from said first position to said second position to compresssaid spring, said spring being extendable on disengagement of saidclutch means to drive said nut longitudinally along said screw to saidfirst position.

8. An actuating device as set forth in claim 7, characterized in that apair of guide rods are mounted longitudinall within said housing, saidpressure plate being provided wi holes therein through which said rodspass in sliding engagement therewith.

9. A valve actuator comprising: a body affixed to a valve; a ball-screwmechanism comprising a screw mounted within said body for rotation onlyand a nut engageable with said screw through ball bearing means andlongitudinally movable along said screw on rotation of said screw; yokemeans rotatably mounted in said body and adapted for attachment to thestem of said valve; a mechanism connecting said nut and said yokeadapted to convert longitudinal movement of said nut to rotationalmovement of said valve stem; an electric motor connected to said screwthrough disengageable clutch means for rotation of said screw to drivesaid nut longitudinally therealong from a first position to a secondposition.

10. A valve actuator as set forth in claim 9, characterized by a springreturn assembly attached to said body having a spring exerting a forcebiasing said nut in a direction toward said first position whereby ondisengagement of said clutch said nut is driven along said screw fromsaid second position toward said first position.

11. A valve actuator as set forth in claim 10, characterized in thatsaid spring is compressed between one end of an elongated housing and apressure plate, said pressure plate being connected to said nut by atube surrounding a portion of said screw.

12. A valve actuator as set forth in claim 11, characterized in thatsaid spring return assembly is provided with guide means in engagementwith said pressure plate preventing rotation thereof but permittinglongitudinal movement of said plate within said housing.

13. An actuating device comprising: a housing portion capable of beingaffixed to a device to be actuated, a threaded first member mountedwithin said housing for rotation only, and a threaded second memberengageable with said first member and movable therealong on rotation ofsaid first member; a yoke device rotatably mounted in said housing andadapted to be attached to said device to be actuated; mechanismconnecting said second member with said yoke device adapted to translatelongitudinal movement of said second member into rotational movement ofsaid yoke device; motor means connected to said first threaded memberthrough disengageable clutch means for rotation of said first member andthereby causing said yoke device to rotate; and further including aspring device tending to bias said yoke device toward a first position.

14. The device of claim 13 and including combination means to causeconnection and disconnection of said motor means through said clutchmeans, said clutch means including a pair of interlocking jaws withteeth of such configuration as to permit rotation of said first memberby said motor means in only one direction.

15. The device of claim 14 wherein on said combination means beingactivated, and said motor means deactivated, the force exerted by saidspring device is insufficient to cause rotation of said first member.

16. The device of claim 14, wherein said combination means, onactivation, causes movement of one of said clutch jaws into interlockingconnection with other jaw, and, on deactivation of such combinationmeans, causes said one jaw to move out of such engagement.

17. The device of claim 16 wherein said combination means includes asolenoid.

1. An actuating device comprising: a ball-screw arrangement having ascrew with external thread grooves and a nut with internal threadgrooves engageable with said screw through ball bearings cooperativelyreceived within said external and internal thread grooves, said nutbeing longitudinally movable along said screw on rotation of said screwrelative thereto; support means on which said screw is mounted forrotation only; power means connected to said screw for rotation thereofto drive said nut longitudinally thereon from a first to a secondposition; a rotatable member mounted on said support means adapted forattachment to apparatus to be actuated; a mechanism connecting said nutand said rotating member adapted to convert longitudinal movement ofsaid nut to rotary motion of said rotatable member; spring means mountedso as to bias said nut toward said first position; said power meansbeing connected to said screw through clutch means, said clutch meansbeing disengageable to allow rotation of said screw, said spring meansbeing adapted to force said nut along said screw from said secondposition toward said first position when said clutch is disengaged. 2.An actuating device comprising: a ball-screw arrangement having a screwwith external thread grooves and a nut with internal thread groovesengageable with said screw through ball bearings cooperatively receivedwithin said external and internal thread grooves, said nut beinglongitudinally movable along said screw on rotation of said screwrelative thereto; support means on which said screw is mounted forrotation only; power means connected to said screw for rotation thereofto drive said nut longitudinally thereon from a first position to asecond position; a rotatable member mounted on said support meansadapted for attachment to apparatus to be actuated; a mechanismconnecting said nut and said rotating member adapted to convertlongitudinal movement of said nut to rotary motion of said rotatablemember; spring means mounted so as to bias said nut toward said firstposition; said spring means comprises a cylindrical housing attached tosaid support means and a helical spring mounted in said housing, one endof said spring bearing against a pressure plate, said pressure platebeing connected to said nut by shaft means so that on movement of saidnut from said first position to said second position said pressure platemoves longitudinally within said housing to compress said spring.
 3. Anactuating device as set forth in claim 2, characterized by a pair ofrods fixedly and longitudinally mounted within said housing, saidpressure plate having a pair of holes through which said rods pass insliding engagement.
 4. An actuating device as set forth in claim 2characterized in that said shaft means comprises a hollow tubesurrounding a portion of said screw and longitudinally movable thereonwith said nut.
 5. An actuating device comprising: body means, aball-screw mechanism having a screw mounted longitudinally within saidbody for rotation only and a nut engageable with said screw through ballbearing means and longitudinally movable along said screw on rotation ofsaid screw; yoke means mounted in said body means for rotation on anaxis substantially perpendicular to said screw and adapted forattachment to apparatus to be actuated; a mechanism coNnecting said nutand said yoke adapted to convert longitudinal movement of said nut torotary movement of said yoke; power means connected to said screw forrotation thereof to cause said nut to move longitudinally therealongfrom a first position to a second position; spring means mounted on saidbody adapted to bias said nut toward said first position, said powermeans being connected to said screw by clutch means, said clutch meansbeing disengageable when said nut is in said second position to allowsaid spring means to return said nut toward said first position.
 6. Anactuating device as set forth in claim 5, characterized in that saidpower means comprises an electric motor and said clutch means comprisessleeve means, mounted on the end of said screw for limited longitudinalmovement, and a solenoid, said sleeve means being connected to saidsolenoid by a pivoting link, said solenoid being adapted, whenenergized, to pivot said link and move said sleeve means longitudinallyinto engagement with a portion of said clutch connected to said electricmotor.
 7. An actuating device as set forth in claim 5, characterized inthat said spring means comprises a spring mounted in an elongatedhousing attached to said body, said spring bearing against a pressureplate which is connected to said nut by a tube surrounding said screw,said tube and said pressure plate being longitudinally movable onmovement of said nut from said first position to said second position tocompress said spring, said spring being expandable on disengagement ofsaid clutch means to drive said nut longitudinally along said screw tosaid first position.
 8. An actuating device as set forth in claim 7,characterized in that a pair of guide rods are mounted longitudinallywithin said housing, said pressure plate being provided with holestherein through which said rods pass in sliding engagement therewith. 9.A valve actuator comprising: a body affixed to a valve; a ball-screwmechanism comprising a screw mounted within said body for rotation onlyand a nut engageable with said screw through ball bearing means andlongitudinally movable along said screw on rotation of said screw; yokemeans rotatably mounted in said body and adapted for attachment to thestem of said valve; a mechanism connecting said nut and said yokeadapted to convert longitudinal movement of said nut to rotationalmovement of said valve stem; an electric motor connected to said screwthrough disengageable clutch means for rotation of said screw to drivesaid nut longitudinally therealong from a first position to a secondposition.
 10. A valve actuator as set forth in claim 9, characterized bya spring return assembly attached to said body having a spring exertinga force biasing said nut in a direction toward said first positionwhereby on disengagement of said clutch said nut is driven along saidscrew from said second position toward said first position.
 11. A valveactuator as set forth in claim 10, characterized in that said spring iscompressed between one end of an elongated housing and a pressure plate,said pressure plate being connected to said nut by a tube surrounding aportion of said screw.
 12. A valve actuator as set forth in claim 11,characterized in that said spring return assembly is provided with guidemeans in engagement with said pressure plate preventing rotation thereofbut permitting longitudinal movement of said plate within said housing.13. An actuating device comprising: a housing portion capable of beingaffixed to a device to be actuated, a threaded first member mountedwithin said housing for rotation only, and a threaded second memberengageable with said first member and movable therealong on rotation ofsaid first member; a yoke device rotatably mounted in said housing andadapted to be attached to said device to be actuated; mechanismconnecting said second member with said yoke device adapted to translatelongitudinal movement of said second member into rotational movemeNt ofsaid yoke device; motor means connected to said first threaded memberthrough disengageable clutch means for rotation of said first member andthereby causing said yoke device to rotate; and further including aspring device tending to bias said yoke device toward a first position.14. The device of claim 13 and including combination means to causeconnection and disconnection of said motor means through said clutchmeans, said clutch means including a pair of interlocking jaws withteeth of such configuration as to permit rotation of said first memberby said motor means in only one direction.
 15. The device of claim 14wherein on said combination means being activated, and said motor meansdeactivated, the force exerted by said spring device is insufficient tocause rotation of said first member.
 16. The device of claim 14, whereinsaid combination means, on activation, causes movement of one of saidclutch jaws into interlocking connection with other jaw, and, ondeactivation of such combination means, causes said one jaw to move outof such engagement.
 17. The device of claim 16 wherein said combinationmeans includes a solenoid.